Bending Failure Assessment of C/C Composite byCompeting Risk Theory

摘要

Bending failure of two-dimensional carbon fiber reinforced carbon matrix composite was studied by bothexperimental and analytical approaches. In the experiment, bending tests and observation of failure surfaces wereperformed to clarify the fundamental fracture modes of the C/C composite. From the surface observation, threekinds of fundamental fracture modes were observed; these were tensile fracture mode, compressive fracture modeand shear fracture mode. In the analysis, the risk-based statistical fracture theory, so-called the competing risktheory was applied to clarify the bending failure taking account of the competition of these fracture modes.Parameters used in the theory on these fundamental fracture modes were determined by additional experiments, andthe theory was applied to the bending failure prediction. As a result of this study, it is concluded that the bendingfailure was well predicted by the competing risk theory, and that the theory would be possible to predict the strengthunder stress gradient condition. Furthermore, a new strength prediction method combined with FEM code, which isapplicable to arbitrary shaped structures with stress gradient, was proposed in this paper.